Method of manufacturing a semiconductor device and apparatus for manufacturing the semiconductor device

ABSTRACT

A method of manufacturing a semiconductor device includes dividing a number of dies along an x axis in a die matrix in each exposure field in an exposure field matrix delineated on the semiconductor substrate, wherein the x axis is parallel to one edge of a smallest rectangle enclosing the exposure field matrix. A number of dies is divided along a y axis in the die matrix, wherein the y axis is perpendicular to the x axis. Sequences SNx0, SNx1, SNx, SNxr, SNy0, SNy1, SNy, and SNyr are formed. p*(Nbx+1)−2 stepping operations are performed in a third direction and first sequence exposure/stepping/exposure operations and second sequence exposure/stepping/exposure operations are performed alternately between any two adjacent stepping operations as well as before a first stepping operation and after a last stepping operation. A distance of each stepping operation in order follows the sequence SNx.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 16/525,510, filed Jul. 29, 2019, now U.S. Pat. No. 10,866,525, whichclaims priority to U.S. Provisional Patent Application No. 62/712,953,filed Jul. 31, 2018, the entire disclosures of each of which areincorporated herein by reference.

BACKGROUND

As consumer devices have gotten smaller and smaller in response toconsumer demand, the individual components of these devices havenecessarily decreased in size as well. Semiconductor devices, which makeup a major component of devices such as mobile phones, computer tablets,and the like, have been pressured to become smaller and smaller, with acorresponding pressure on the individual devices (e.g., transistors,resistors, capacitors, etc.) within the semiconductor devices to also bereduced in size. The decrease in size of devices has been met withadvancements in semiconductor manufacturing techniques such aslithography.

For example, the wavelength of radiation used for lithography hasdecreased from ultraviolet to deep ultraviolet (DUV) and, more recentlyto extreme ultraviolet (EUV). Further decreases in component sizerequire further improvements in resolution of lithography which areachievable using extreme ultraviolet lithography (EUVL). EUVL employsradiation having a wavelength of about 1-100 nm.

As the semiconductor industry has progressed into nanometer technologyprocess nodes in pursuit of higher device density, higher performance,and lower costs, there have been challenges in reducing semiconductorfeature size.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 shows an extreme ultraviolet lithography tool according to anembodiment of the disclosure.

FIG. 2 shows a schematic diagram of a detail of an extreme ultravioletlithography tool according to an embodiment of the disclosure.

FIG. 3 is a cross-sectional view of a reflective mask according toembodiments of the disclosure.

FIGS. 4A, 4B, 4C, and 4D illustrate column-wise folding exposureoperations as viewed in plan view.

FIGS. 5A, 5B, 5C, and 5D illustrate row-wise folding exposure operationsas viewed in plan view.

FIG. 6 shows a semiconductor wafer with a plurality of dies according toan embodiment of the disclosure.

FIG. 7 shows a photolithography apparatus according to an embodiment ofthe disclosure.

FIGS. 8A and 8B show an embodiment of a controller for aphotolithography apparatus according to an embodiment of the disclosure.

FIG. 9 is a flow chart illustrating a method of manufacturing asemiconductor device according to an embodiment of the presentdisclosure.

FIG. 10 is a flow chart illustrating a method of manufacturing asemiconductor device according to an embodiment of the presentdisclosure.

FIG. 11 is a flow chart illustrating a method of manufacturing asemiconductor device according to an embodiment of the presentdisclosure.

FIG. 12 is a flow chart illustrating a method of manufacturing asemiconductor device according to an embodiment of the presentdisclosure.

FIG. 13 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 14 is a flow chart illustrating a method of manufacturing asemiconductor device according to an embodiment of the presentdisclosure.

FIG. 15 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 16 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 17 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 18 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 19 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 20 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 21 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 22 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 23 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 24 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 25 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 26 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 27 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 28 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 29 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 30 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 31 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 32 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 33 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 34 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 35 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 36 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 37 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 38 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 39 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 40 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 41 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 42 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 43 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 44 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 45 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 46 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 47 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 48 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 49 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 50 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 51 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 52 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 53 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 54 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 55 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 56 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 57 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 58 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 59 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 60 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 61 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 62 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 63 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 64 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 65 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 66 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 67 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 68 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 69 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 70 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 71 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 72 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 73 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 74 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 75 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 76 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 77 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 78 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 79 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 80 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 81 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 82 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 83 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 84 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 85 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 86 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 87 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 88 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 89 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 90 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 91 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 92 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 93 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 94 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 95 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 96 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 97 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 98 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 99 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 100 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 101 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 102 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 103 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 104 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 105 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 106 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 107 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 108 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 109 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

FIG. 110 shows one of various sequential operations in a method ofexposing a photoresist layer on a semiconductor substrate according toan embodiment of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the disclosure. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The device may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.”

The present disclosure is generally related to extreme ultraviolet (EUV)lithography systems and methods. In an EUVL tool, a laser-producedplasma (LPP) generates extreme ultraviolet radiation which is used toimage a photoresist-coated substrate. In an EUV tool, an excitationlaser heats metal (e.g., tin, lithium, etc.) target droplets in the LPPchamber to ionize the droplets to plasma which emits the EUV radiation.For reproducible generation of EUV radiation, the target dropletsarriving at the focal point (also referred to herein as the “zone ofexcitation”) have to be substantially the same size and arrive at thezone of excitation at the same time as an excitation pulse from theexcitation laser arrives. Thus, stable generation of target dropletsthat travel from the target droplet generator to the zone of excitationat a uniform (or predictable) speed contributes to efficiency andstability of the LPP EUV radiation source.

FIG. 1 is a schematic view of an EUV lithography tool with a laserproduction plasma (LPP) based EUV radiation source, constructed inaccordance with some embodiments of the present disclosure. The EUVlithography system includes an EUV radiation source 100 to generate EUVradiation, an exposure device 200, such as a scanner, and an excitationlaser source 300. As shown in FIG. 1, in some embodiments, the EUVradiation source 100 and the exposure device 200 are installed on a mainfloor MF of a clean room, while the excitation laser source 300 isinstalled in a base floor BF located under the main floor. Each of theEUV radiation source 100 and the exposure device 200 are placed overpedestal plates PP1 and PP2 via dampers DP1 and DP2, respectively. TheEUV radiation source 100 and the exposure device 200 are coupled to eachother by a coupling mechanism, which may include a focusing unit.

The EUV lithography tool is designed to expose a resist layer by EUVlight (also interchangeably referred to herein as EUV radiation). Theresist layer is a material sensitive to the EUV light. The EUVlithography system employs the EUV radiation source 100 to generate EUVlight, such as EUV light having a wavelength ranging between about 1 nmand about 100 nm. In one particular example, the EUV radiation source100 generates an EUV light with a wavelength centered at about 13.5 nm.In the present embodiment, the EUV radiation source 100 utilizes amechanism of laser-produced plasma (LPP) to generate the EUV radiation.

The exposure device 200 includes various reflective optic components,such as convex/concave/flat mirrors, a mask holding mechanism includinga mask stage, and wafer holding mechanism. The EUV radiation EUVgenerated by the EUV radiation source 100 is guided by the reflectiveoptical components onto a mask secured on the mask stage. In someembodiments, the mask stage includes an electrostatic chuck (e-chuck) tosecure the mask.

FIG. 2 is a simplified schematic diagram of a detail of an extremeultraviolet lithography tool according to an embodiment of thedisclosure showing the exposure of photoresist coated substrate 210 witha patterned beam of EUV light. The exposure device 200 is an integratedcircuit lithography tool such as a stepper, scanner, step and scansystem, direct write system, device using a contact and/or proximitymask, etc., provided with one or more optics 205 a, 205 b, for example,to illuminate a patterning optic 205 c, such as a mask, with a beam ofEUV light, to produce a patterned beam, and one or more reductionprojection optics 205 d, 205 e, for projecting the patterned beam ontothe substrate 210. A mechanical assembly (not shown) may be provided forgenerating a controlled relative movement between the substrate 210 andpatterning optic 205 c. As further shown in FIG. 2, the EUVL toolincludes an EUV light source 100 including an EUV light radiator ZEemitting EUV light in a chamber 105 that is reflected by a collector 110along a path into the exposure device 200 to irradiate the substrate210.

As used herein, the term “optic” is meant to be broadly construed toinclude, and not necessarily be limited to, one or more components whichreflect and/or transmit and/or operate on incident light, and includes,but is not limited to, one or more lenses, windows, filters, wedges,prisms, grisms, gratings, transmission fibers, etalons, diffusers,homogenizers, detectors and other instrument components, apertures,axicons and mirrors including multi-layer mirrors, near-normal incidencemirrors, grazing incidence mirrors, specular reflectors, diffusereflectors and combinations thereof. Moreover, unless otherwisespecified, neither the term “optic”, as used herein, are meant to belimited to components which operate solely or to advantage within one ormore specific wavelength range(s) such as at the EUV output lightwavelength, the irradiation laser wavelength, a wavelength suitable formetrology or any other specific wavelength.

Because gas molecules absorb EUV light, the lithography system for theEUV lithography patterning is maintained in a vacuum or a-low pressureenvironment to avoid EUV intensity loss.

In the present disclosure, the terms mask, photomask, and reticle areused interchangeably. In the present embodiment, the patterning optic205 c shown in FIG. 3 is a reflective mask. In an embodiment, thereflective reticle 205 c includes a substrate 30 with a suitablematerial, such as a low thermal expansion material or fused quartz, asshown in FIG. 3. In various examples, the material includes TiO₂ dopedSiO₂, or other suitable materials with low thermal expansion. Thereflective reticle 205 c includes multiple reflective multiple layers(ML) 35 deposited on the substrate. The ML 35 includes a plurality offilm pairs, such as molybdenum-silicon (Mo/Si) film pairs (e.g., a layerof molybdenum 39 above or below a layer of silicon 37 in each filmpair). Alternatively, the ML 35 may include molybdenum-beryllium (Mo/Be)film pairs, or other suitable materials that are configured to highlyreflect the EUV light. The mask 205 c may further include a cappinglayer 40, such as ruthenium (Ru), disposed on the ML for protection. Themask further includes an absorption layer (or absorber) 45, such as atantalum boron nitride (TaBN) layer, and/or a tantalum boron oxide(TaBO) layer, deposited over the ML 35. The absorption layer 45 ispatterned to define a layer of an integrated circuit (IC). Thereflective mask 205 c includes a conductive backside coating 60.Alternatively, another reflective layer may be deposited over the ML 35and is patterned to define a layer of an integrated circuit, therebyforming an EUV phase shift reticle. In some embodiments, the reflectivemask 205 c includes a border 65 etched down to the substrate 30surrounding the pattern 55, also known as a black border 65, to define acircuit area to be imaged and a peripheral area not to be imaged. Theblack border reduces light leakage in some embodiments.

In various embodiments of the present disclosure, the photoresist-coatedsubstrate 210 is a semiconductor wafer, such as a silicon wafer or othertype of wafer to be patterned.

The EUVL tool further include other modules or is integrated with (orcoupled with) other modules in some embodiments.

As shown in FIG. 1, the EUV radiation source 100 includes a targetdroplet generator 115 and a LPP collector 110, enclosed by a chamber105. In some embodiments, the target droplet generator 115 includes areservoir to hold a source material and a nozzle 120 through whichtarget droplets DP of the source material are supplied into the chamber105.

In some embodiments, the target droplets DP are droplets of tin (Sn),lithium (Li), or an alloy of Sn and Li. In some embodiments, the targetdroplets DP each have a diameter in a range from about 10 microns (μall)to about 100 μm. For example, in an embodiment, the target droplets DPare tin droplets, having a diameter of about 10 μm to about 100 μm. Inother embodiments, the target droplets DP are tin droplets having adiameter of about 25 μm to about 50 μm. In some embodiments, the targetdroplets DP are supplied through the nozzle 120 at a rate in a rangefrom about 50 droplets per second (i.e., an ejection-frequency of about50 Hz) to about 50,000 droplets per second (i.e., an ejection-frequencyof about 50 kHz). In some embodiments, the target droplets DP aresupplied at an ejection-frequency of about 100 Hz to about 25 kHz. Inother embodiments, the target droplets DP are supplied at an ejectionfrequency of about 500 Hz to about 10 kHz. The target droplets DP areejected through the nozzle 127 and into a zone of excitation ZE at aspeed in a range of about 10 meters per second (m/s) to about 100 m/s insome embodiments. In some embodiments, the target droplets DP have aspeed of about 10 m/s to about 75 m/s. In other embodiments, the targetdroplets have a speed of about 25 m/s to about 50 m/s.

Referring back to FIG. 1, an excitation laser LR2 generated by theexcitation laser source 300 is a pulse laser. The laser pulses LR2 aregenerated by the excitation laser source 300. The excitation lasersource 300 may include a laser generator 310, laser guide optics 320 anda focusing apparatus 330. In some embodiments, the laser source 310includes a carbon dioxide (CO2) or a neodymium-doped yttrium aluminumgarnet (Nd:YAG) laser source with a wavelength in the infrared region ofthe electromagnetic spectrum. For example, the laser source 310 has awavelength of 9.4 μm or 10.6 μm, in an embodiment. The laser light LR1generated by the laser generator 300 is guided by the laser guide optics320 and focused into the excitation laser LR2 by the focusing apparatus330, and then introduced into the EUV radiation source 100.

In some embodiments, the excitation laser LR2 includes a pre-heat laserand a main laser. In such embodiments, the pre-heat laser pulse(interchangeably referred to herein as the “pre-pulse) is used to heat(or pre-heat) a given target droplet to create a low-density targetplume with multiple smaller droplets, which is subsequently heated (orreheated) by a pulse from the main laser, generating increased emissionof EUV light.

In various embodiments, the pre-heat laser pulses have a spot size about100 μm or less, and the main laser pulses have a spot size in a range ofabout 150 μm to about 300 μm. In some embodiments, the pre-heat laserand the main laser pulses have a pulse-duration in the range from about10 ns to about 50 ns, and a pulse-frequency in the range from about 1kHz to about 100 kHz. In various embodiments, the pre-heat laser and themain laser have an average power in the range from about 1 kilowatt (kW)to about 50 kW. The pulse-frequency of the excitation laser LR2 ismatched with the ejection-frequency of the target droplets DP in anembodiment.

The laser light LR2 is directed through windows (or lenses) into thezone of excitation ZE. The windows adopt a suitable materialsubstantially transparent to the laser beams. The generation of thepulse lasers is synchronized with the ejection of the target droplets DPthrough the nozzle 120. As the target droplets move through theexcitation zone, the pre-pulses heat the target droplets and transformthem into low-density target plumes. A delay between the pre-pulse andthe main pulse is controlled to allow the target plume to form and toexpand to an optimal size and geometry. In various embodiments, thepre-pulse and the main pulse have the same pulse-duration and peakpower. When the main pulse heats the target plume, a high-temperatureplasma is generated. The plasma emits EUV radiation EUV, which iscollected by the collector mirror 110. The collector 110 furtherreflects and focuses the EUV radiation for the lithography exposingprocesses performed through the exposure device 200. The droplet catcheris used for catching excessive target droplets. For example, some targetdroplets may be purposely missed by the laser pulses.

Referring back to FIG. 1, the collector 110 is designed with a propercoating material and shape to function as a mirror for EUV collection,reflection, and focusing. In some embodiments, the collector 110 isdesigned to have an ellipsoidal geometry. In some embodiments, thecoating material of the collector 100 is similar to the reflectivemultilayer of the EUV mask. In some examples, the coating material ofthe collector 110 includes a ML (such as a plurality of Mo/Si filmpairs) and may further include a capping layer (such as Ru) coated onthe ML to substantially reflect the EUV light. In some embodiments, thecollector 110 may further include a grating structure designed toeffectively scatter the laser beam directed onto the collector 110. Forexample, a silicon nitride layer is coated on the collector 110 and ispatterned to have a grating pattern.

In such an EUV radiation source, the plasma caused by the laserapplication creates physical debris, such as ions, gases, and atoms ofthe droplet, as well as the desired EUV radiation. It is necessary toprevent the accumulation of material on the collector 110 and also toprevent physical debris exiting the chamber 105 and entering theexposure device 200.

As shown in FIG. 1, in the present embodiment, a buffer gas is suppliedfrom a first buffer gas supply 130 through the aperture in collector 110by which the pulse laser is delivered to the tin droplets. In someembodiments, the buffer gas is H₂, He, Ar, N₂, or another inert gas. Incertain embodiments, H₂ used as H radicals generated by ionization ofthe buffer gas can be used for cleaning purposes. The buffer gas canalso be provided through one or more second buffer gas supplies 135toward the collector 110 and/or around the edges of the collector 110.Further, the chamber 105 includes one or more gas outlets 140 so thatthe buffer gas is exhausted outside the chamber 105.

Hydrogen gas has low absorption to the EUV radiation. Hydrogen gasreaching the coating surface of the collector 110 reacts chemically witha metal of the droplet forming a hydride, e.g., metal hydride. When tin(Sn) is used as the droplet, stannane (SnH₄), which is a gaseousbyproduct of the EUV generation process, is formed. The gaseous SnH₄ isthen pumped out through the outlet 140.

It is desirable to improve resolution of the EUVL operation in order toincrease the yield of semiconductor devices. In some cases, patterndefects in a mask or particulate contamination on a mask surface causedefects in a photoresist layer pattern when the photomask with thedefect or contaminant is used to form the pattern in the photoresistlayer. To improve exposure resolution in an EUVL operation and to avoiddefective patterns due to particles or mask defects, multiple exposuresof the photoresist-covered wafer is performed. Methods, according toembodiments of the disclosure, realize the exposure of the patterns of achip on a wafer by accumulating the mask images from N mask regions, oneach of which there are the same mask patterns.

In some embodiments, a p*q folding exposure is performed using a stepand scan exposure system. A folding exposure includes repeatedlyexposing a full field image, while stepping the mask relative to thephotoresist-coated wafer being exposed a stepping distance of a die sizeor multiples of the die size between each exposure. The folding exposureis column-wise in some embodiments and row-wise in other embodiments.Examples of folding exposures are illustrated in FIGS. 4A to 5D.

FIGS. 4A to 4D illustrate column-wise folding exposure operations asviewed in plan view over a wafer (not shown). The star indicates thestarting point of a sequence of exposure/stepping/exposure operations,and the arrows show the direction of motion of a wafer stage. Forexample, in FIG. 4A, the exposure/stepping/exposure operation starts inthe upper left corner of the wafer (not shown) and theexposure/stepping/exposure proceeds in the direction (y axis) of thevertical arrow. At the end of the exposure/stepping/exposure sequencealong the y-axis, the wafer stage is stepped to the right along thex-axis (horizontal arrow), and another sequence ofexposure/stepping/exposure operations is performed along the y axis inthe opposite direction as the first sequence ofexposure/stepping/exposure operations. At the end ofexposure/stepping/exposure operations along the y axis, the wafer stageis again stepped to the right. The alternating process ofexposure/stepping/exposure operations and stepping to the right iscontinued until a desired portion of the wafer is exposed. In anotherembodiment, as shown in FIG. 4B the exposure/stepping/exposure operationstarts in the upper right corner of the wafer and an alternating processof exposure/stepping/exposure operations and stepping to the left isperformed in a similar manner as explained with reference to FIG. 4A. Inanother embodiment, as shown in FIG. 4C the exposure/stepping/exposureoperation starts in the lower left corner of the wafer and analternating process of exposure/stepping/exposure operations andstepping to the left is performed in a similar manner as explained withreference to FIG. 4A. In another embodiment, as shown in FIG. 44 theexposure/stepping/exposure operation starts in the lower right corner ofthe wafer and an alternating process of exposure/stepping/exposureoperations and stepping to the left is performed in a similar manner asexplained with reference to FIG. 4A.

FIGS. 5A to 5D illustrate row-wise folding exposure operations as viewedin plan view over a wafer (not shown). The star indicates the startingpoint of a sequence of exposure/stepping/exposure operations, and thearrows show the direction of motion of a wafer stage. For example, inFIG. 5A, the exposure/stepping/exposure operation starts in the upperleft corner of the wafer (not shown) and the exposure/stepping/exposureproceeds in the direction (x axis) of the horizontal arrow. At the endof the exposure/stepping/exposure sequence along the x-axis, the waferstage is stepped down along the y-axis (vertical arrow), and anothersequence of exposure/stepping/exposure operations is performed along thex axis in the opposite direction as the first sequence ofexposure/stepping/exposure operations. At the end ofexposure/stepping/exposure operations along the x axis, the wafer stageis again stepped down in the vertical direction. The alternating processof exposure/stepping/exposure operations and stepping down is continueduntil a desired portion of the wafer is exposed. In another embodiment,as shown in FIG. 5B the exposure/stepping/exposure operation starts inthe upper right corner of the wafer and an alternating process ofexposure/stepping/exposure operations along the x axis and stepping downalong the y axis is performed in a similar manner as explained withreference to FIG. 5A. In another embodiment, as shown in FIG. 5C theexposure/stepping/exposure operation starts in the lower left corner ofthe wafer and an alternating process of exposure/stepping/exposureoperations along the x axis and stepping up along the y axis isperformed in a similar manner as explained with reference to FIG. 5A. Inanother embodiment, as shown in FIG. 5D the exposure/stepping/exposureoperation starts in the lower right corner of the wafer and analternating process of exposure/stepping/exposure operations andstepping up performed in a similar manner as explained with reference toFIG. 5A.

Arranging the dies as a matrix there are Nax*Nay dies in an exposurefield F (or field, i.e., the one-time exposure region. As shown in FIG.6, the die size along the x-axis is Dx and the die size along the y-axisis Dy. The fields F are arranged as a matrix on the wafer, however,those rectangular shaped fields completely or partially outside thecircular shaped wafer 210 are removed from the matrix.

In the matrix of fields, there are Nbx columns. In the first column(leftmost column, there are Nby fields and in the second column (columnnext to the first column), there are Nby fields, and so on for eachcolumn. The field size along the x-axis is Fx, and the field size alongthe y-axis column is Fy. In some embodiments, Nax is divided into pterms: Nax_1, Nax_2, . . . , Nax_p, where (Nax_1+Nax_2+ . . .+Nax_p=Nax). A sequence SNx0 is formed, by repeating Nbx+1 times the pterms in order. Nbx is an integer closest to Rx/Fx, where Rx is a sizealong the x axis of a smallest rectangle enclosing the exposure fieldmatrix, called the exposure field matrix enclosure, and Fx is anexposure field size along the x axis. Eliminating the first and lastelements of SNx0 results in a new sequence SNx1. A sequence SNx isformed by multiplying each element of SNx1 by Dx, where Dx is a die sizealong the x axis. By reversing the order of SNx, a sequence SNxr isformed.

In some embodiments, Nay is divided into q terms: Nay_1, Nay_2, . . . ,Nay_q, where (Nay_1+Nay_2+ . . . +Nay_q=Nay). A sequence SNy0 is formed,by repeating Nby+1 times the q terms in order. Nby is an integer closestto Ry/Fy, where Ry is a size along the y axis of a smallest rectangleenclosing the exposure field matrix, called the exposure field matrixenclosure, and Fy is an exposure field size along the y axis.Eliminating the first and last elements of SNy0 results in a newsequence SNy1. A sequence SNy is formed by multiplying each element ofSNy1 by Dy, where Dy is a die size along the y axis. By reversing theorder of SNy, a sequence SNyr is formed.

To achieve a p*q folding exposure, p≥Nax and q≥Nay are needed in someembodiments.

In some embodiments, a sequence SFy0 is formed, where Sfy0: F−, F+, F−,F+, . . . , for a total of q*(Nby[1]+1) terms. Where F− refers to anexposure done at a focus position above the target focus position and F+refers to an exposure done at a focus position done below the targetfocus position. Eliminating the last element of SFy0 results in a newsequence SFy1. Similarly, SFy2, SFy3, SFyNbx can be generated.

In some embodiments, a method of exposing a photoresist layer includesmoving the wafer stage to a starting position and then performing anexposure such that Nax_1*Nay_1 dies around the staring position, forexample a lower-left corner of the lowest field in the first column, areexposed. The wafer stage performs q*(Nby1+1)−2 upward steppings, thedistance of each of which in order follows the sequence SNy1. After eachstepping, an exposure is performed. The focus setting of each of theexposures follows the sequence SFy1. For example, the focus setting ofthe first exposure is the first element in SFy1; the focus setting ofthe second exposure is the second element in SFy1, . . . , etc.

Next, the wafer stage is stepped rightward by a distance following thefirst element of SNx, and then an exposure is performed. After therightward stepping and exposure, the wafer stage performs q*(Nby1+1)−2downward steppings, the distance of each of which in order follows thesequence SNyr1. After each stepping, an exposure is performed. The focussetting of each of the exposures order follows the sequence SFy1.

The exposure and stepping operations are continued until the firstcolumn of fields is traversed p times, either upward or downward. Thenthe wafer stage is stepped rightward by a distance following the p-thelement of SNx, and an exposure is performed.

In some embodiments, the total dose accumulated in each die is withinabout 75% to about 125% of the target dose. In some embodiments, theexposure latitude is larger than 25%.

The above-described exposure and stepping operations are performed in acolumn-wise folding exposure in some embodiments and in a row-wisefolding exposure in other embodiments.

For example, in some embodiments, each die on the photoresist-coatedwafer is exposed four times with the same pattern, using a differentportion of the mask. In some embodiments, the exposure mask includes thesame pattern in four adjacent locations on the mask, and as the wafer ismoved relative to the exposure beam, each die is exposed four times tothe same pattern. To prevent overexposure of a given die, the exposuredose from each exposure is one-fourth the desired total exposure dose.The reduced exposure dose at each exposure is achieved by scanning theexposure beam quicker at each exposure, in some embodiments. Thus, thephotoresist-coated wafer is exposed for a shorter period of time duringeach scanning exposure. For example, the scanning beam can be movedrelative to the photoresist layer at four times the normal speed so thatat each exposure each die is exposed for one-fourth the total exposuretime. In some embodiments, the reduced exposure dose is achieved bymoving the wafer stage quicker at each scanning exposure. It is notlikely that a defect in or a particle contaminant on one pattern wouldbe found in the same location in another pattern of the mask. Becauseeach exposure is below the desired total exposure, isolated defects orparticles on one portion of the mask will not be imaged into thephotoresist layer. The cumulative exposure doses of the multipleexposures using different portions of the mask having the same circuitor chip pattern will reproduce the pattern in the photoresist withoutimaging the isolated defects or particles, according to embodiments ofthe disclosure.

The exposure mask is not limited to four adjacent same patterns. Othermask arrangements may include more than four adjacent same patterns. Insome embodiments, there are five, six, seven, eight, or more adjacentsame patterns. The present disclosure is not limited to four exposuresof each die, and the multiple number of exposures can be two, three, orfive or more. The multiple exposures by different portions of the maskwith the same pattern smooths out any defects that may be present in agiven position of the mask in some embodiments.

In some embodiments, each of the multiple exposures is performed at adifferent focus position. The different focus positions are achieved bymoving the wafer stage closer to or further away from the imaging lightsource or mask. In some embodiments, the wafer stage is tilted duringscanning exposure to achieve an image formed at a range of focuspositions. In some embodiments, the wafer stage is tilted by up to about50 micro radians with respect to the horizontal direction during theexposing of one field. During a scanning exposure, the wafer stage iseither tilted up (+) or tilted down (−), but not both, in someembodiments. In some embodiments, the wafer stage is moved in a verticaldirection relative to the imaging light source or mask to move the wafercloser to or further away from the imaging light source or mask. In someembodiments, the wafer stage is moved from −50 nm to +50 nm relative tothe target or the best focus position during the exposing of one field.

Exposing the same area of the photoresist-coated wafer 210 at differentdepths of focus is known as focus latitude enhanced exposure (FLEX). Ina FLEX operation, multiple exposures in several different focal planesare used to extend the image contrast of the mask pattern along thelight axis. The FLEX operation can provide a 3× to 4× increase inpattern focus position.

In some embodiments, sub resolution assist features (SRAFs) are providedadjacent the desired pattern on the photomask to improve patternresolution.

A photolithography apparatus 400 according to an embodiment of thedisclosure is illustrated in FIG. 7. A semiconductor substrate 210having a photoresist layer 250 coated thereon is exposed to radiation inthe photolithography apparatus 400. The photoresist coated semiconductorsubstrate is supported by a wafer stage 255. In some embodiments, thephotomask 205 c and the photoresist layer are separated by a distanceDl. The wafer stage 255 is configured to move laterally L or verticallyV relative to a photomask 205 c in some embodiments. The lateral motionL includes motion along the X-axis or the Y-axis (into the page). Thevertical motion V is along the Z-axis. In some embodiments, the waferstage 255 is moved from −XX to +XX or from +XX to −XX, where XX is inthe range from 10 nm to 200 nm relative to photomask 205 c, therebychanging the distance between the photomask 205 c and the photoresistlayer 250. Thus, in some embodiments, the distance between the photomask205 c and the photoresist layer 250 increases or decreases relative tothe initial distance Dl. During a scanning exposure, in someembodiments, the wafer stage is configured to tilt about the X-axis whenthe scanning direction is along the Y-axis. In some embodiments, theangle of tilt about the X-axis is TT, where TT is in the range of about10 to about 200 micro radians.

In some embodiments, the radiation is extreme ultraviolet radiation, andthe photomask 205 c is a reflective EUV photomask. In some embodiments,the extreme ultraviolet radiation is generated in an EUV radiationsource 100, as previously discussed herein. The EUV radiation source 100generates EUV radiation 265 that is directed towards the photomask 205and is reflected off the reflective photomask 205 c. The reflected EUVradiation 270 includes pattern information according to the pattern inthe photomask 205 c. The patterned reflected EUV radiation 270 exposesthe photoresist layer 250 in a patternwise manner, thereby forming alatent pattern in the photoresist layer 250 corresponding to thephotomask pattern. A pattern is formed in the patternwise exposedphotoresist layer by developing the exposed photoresist layer using asuitable developer. The photoresist is a positive-tone resist or anegative-tone resist. In a positive tone photoresist, the exposedportions of the photoresist layer are subsequently removed during thedeveloping operation. In a negative tone photoresist, the unexposedportions of the photoresist layer are subsequently removed during thedeveloping operation.

The pattern in the photoresist is extended into an underlying layerusing a suitable etching operation in some embodiments. The etchingoperation may be a wet etching operation or a dry etching operation.After forming the pattern in the underlying layer, the remainingphotoresist is removed by a suitable photoresist stripping or plasmaashing operation.

In some embodiments, there are additional optics between the EUVradiation source 100 and the photomask 205 c, or between the photomask205 c and the photoresist layer 250, as needed, to further reduce thesize of the pattern on the photoresist layer 250 or focus EUV radiation.

In some embodiments, the motion of the wafer stage 255 and thegeneration of the exposure radiation is controlled by a controller.FIGS. 8A and 8B illustrate a controller 500 according to someembodiments of the present disclosure. In some of the embodiments, thecontroller 500 is a computer system. FIG. 8A is a schematic view of acomputer system that controls the radiation generation and the waferstage motion. All of or a part of the processes, method and/oroperations of the foregoing embodiments can be realized using computerhardware and computer programs executed thereon. The operations includethe motion of the wafer stage, sequence of exposure shots, exposuredose, generation of EUV radiation, including the frequency of Sn dropletgeneration and timing of the laser pulses. In some embodiments, thecomputer system is provided with a computer 501 including an opticaldisk read only memory (e.g., CD-ROM or DVD-ROM) drive 505 and a magneticdisk drive 506, a keyboard 502, a mouse 503, and a monitor 504.

FIG. 8B is a diagram showing an internal configuration of the someembodiments of the controller 500. In FIG. 8B, the computer 501 isprovided with, in addition to the optical disk drive 505 and themagnetic disk drive 506, one or more processors 511, such as amicroprocessing unit (MPU) 511, a ROM 512 in which a program such as aboot up program is stored, a random access memory (RAM) 513 that isconnected to the MPU 511 and in which a command of an applicationprogram is temporarily stored and a temporary storage area is provided,a hard disk 514 in which an application program, a system program, anddata are stored, and a bus 515 that connects the MPU 511, the ROM 512,and the like. Note that the computer 501 may include a network card (notshown) for providing a connection to a LAN.

The program for causing the controller 500 to execute the functions ofthe sequence of the exposure shots, exposure dose, and wafer stagemovement of the foregoing embodiments may be stored in an optical disk521 or a magnetic disk 522, which are inserted into the optical diskdrive 505 or the magnetic disk drive 506, and transmitted to the harddisk 514. Alternatively, the program may be transmitted via a network(not shown) to the computer 501 and stored in the hard disk 514. At thetime of execution, the program is loaded into the RAM 513. The programmay be loaded from the optical disk 521 or the magnetic disk 522, ordirectly from a network. The program does not necessarily have toinclude, for example, an operating system (OS) or a third party programto cause the computer 501 to execute the functions of the photo maskdata generating and merging apparatus in the foregoing embodiments. Theprogram may only include a command portion to call an appropriatefunction (module) in a controlled mode and obtain desired results.

FIG. 9 is a flow chart illustrating a method 600 of manufacturing asemiconductor device according to an embodiment of the presentdisclosure. In operation S605, a photoresist layer 250 is coated on asemiconductor substrate 210. A target total exposure dose is determinedfor the photoresist layer 250 in operation S610, and in operation S615 atarget focus position is determined of the photoresist layer 250. Insome embodiments, the target total exposure dose is an average optimalexposure dose for the photoresist layer 250. In some embodiments, thetarget focus position is the average optimal focus position for thephotoresist layer 250. In some embodiments, the target total exposuredose and target focus position are previously determined, and are storedin a memory. Target total exposure doses and target depths of focus canbe determined and stored for various wafer sizes, photoresistcompositions, and photoresist layer thicknesses. In some embodiments,the stored target total exposure dose and focus position are input tothe controller 500 prior to the exposure operations.

Then, a first portion of the photoresist layer 250 is exposed to a firstexposure dose of extreme ultraviolet radiation at a first focus positionusing a first portion of an extreme ultraviolet mask 205 c in operationS620. In some embodiments, the exposure is a scanning exposure, and thesemiconductor substrate 210 is moved during the scanning exposureoperation so that scanning radiation exposes the desired pattern in thephotoresist layer 250. The semiconductor substrate 210 is subsequentlymoved relative to the extreme ultraviolet mask 205 c in operation S625.The first portion of the photoresist layer 250 is subsequently exposed,in operation S630, to a second exposure dose of extreme ultravioletradiation using a second portion of the mask 205 c at a second focusposition, and a second portion of the photoresist layer 250 is exposedto the second exposure dose at the second focus position using the firstportion of the extreme ultraviolet mask 205 c. The moving of thesemiconductor substrate 210 relative to the mask 205 c between exposureoperations includes moving the wafer stage 255 supporting thesemiconductor closer to or further away from the mask 205 c, e.g.—in avertical direction, or moving (stepping) the wafer stage 255 in alateral direction, e.g.—from one die on the semiconductor substrate 210to another die. During the stepping operation, the wafer stage 255 isstepped so that a same portion of the mask is positioned over adifferent die in a subsequent exposure operation than in a priorexposure operation. The first portion and second portion of thephotoresist layer 250 are exposed simultaneously during the exposureoperation in some embodiments.

Then, in some embodiments, the semiconductor substrate 210 is movedrelative to the mask 205 c, and the first portion of the photoresistlayer 250 is exposed to a third exposure dose of extreme ultravioletradiation at a third focus position using a third portion of the mask205 c, the second portion of the photoresist layer 250 is exposed to thethird exposure dose of extreme ultraviolet radiation at the third focusposition using the second portion of the mask 205 c, and a third portionof the photoresist layer 250 is exposed to the third exposure dose atthe third focus position using the first portion of the mask 205 c inoperation S640. In some embodiments, the first, second, and thirdportions of the photoresist layer 250 are exposed substantiallysimultaneously during the exposure operation.

In some embodiments, the semiconductor substrate 210 is then movedrelative to the mask 205 c in operation S645. In operation S650, thefirst portion of the photoresist layer 250 is exposed to a fourthexposure dose of extreme ultraviolet radiation at a fourth focusposition using a fourth portion of the mask 205 c, the second portion ofthe photoresist layer 250 is exposed to the fourth exposure dose ofextreme ultraviolet radiation at the fourth focus position using thethird portion of the mask 205 c, a third portion of the photoresistlayer 250 is exposed to the fourth exposure dose at the fourth focusposition using the second portion of the mask 205 c, and a fourthportion of the photoresist layer 250 is exposed to the fourth exposuredose of extreme ultraviolet radiation at the fourth focus position usingthe first portion of the mask 205 c. The first, second, third, andfourth portions of the photoresist layer 250 are exposed substantiallysimultaneously during the exposure operation.

In some embodiments, the first portion of the mask 205 c, the secondportion of the mask 205 c, the third portion of the mask 205 c, and thefourth portion of the mask 205 c each have a same circuit or chippattern. Thus, the same pattern images are superimposed in the firstportion of the photoresist layer 250.

In some embodiments, the first exposure dose, the second exposure dose,the third exposure dose, and the fourth exposure dose are different. Insome embodiments, the first exposure dose and the third exposure doseare the same, and the second exposure dose and the fourth exposure doseare the same, and in some embodiments, the first and third exposuredoses are different from the second and fourth exposure doses. In someembodiments, each of the first exposure dose, the second exposure dose,the third exposure dose, and the fourth exposure dose is less than thetarget exposure dose. In some embodiments, a total of all the exposuredoses received by each portion of the photoresist layer is substantiallyequal to the target exposure dose. In some embodiments, each of thefirst, second, third, and fourth exposure doses are about one quarter ofthe target total exposure dose.

In some embodiments, the focus position alternates between above thetarget focus position and below the target focus position duringsuccessive exposures or shots. In some embodiments, the first focusposition is above the target focus position, the second focus positionis below the target focus position, the third focus position is abovethe target focus position, and the fourth focus position is below thetarget focus position. In other embodiments, the first focus position isbelow the target focus position, the second focus position is above thetarget focus position, the third focus position is below the targetfocus position, and the fourth focus position is above the target focusposition.

In some embodiments, the method includes performing additional exposuresteps (shots) such that each portion of the photoresist layer 250 isexposed the same number of times.

FIG. 10 is a flow chart illustrating a method 700 of manufacturing asemiconductor device according to an embodiment of the presentdisclosure. In operation S705, a semiconductor substrate 210 with aphotoresist layer 250 disposed thereon is placed on a wafer stage. Atarget total exposure dose is determined for each portion of thephotoresist layer 250 in operation S710. A target distance separatingthe photoresist layer from an extreme ultraviolet mask 205 c isdetermined in operation S715. In some embodiments, the target totalexposure dose and target distance are previously determined and storedin a memory. The stored target total exposure dose and distance are theninput into the controller 500 prior to the exposure operations. Then, inoperation S720, a first portion of the photoresist layer 250 is exposedto a first exposure dose of extreme ultraviolet radiation using a firstportion of the extreme ultraviolet mask 205 c, wherein the photoresistlayer 250 and the extreme ultraviolet mask 205 c are separated by afirst distance Dl. In some embodiments, the exposure is a scanningexposure. The semiconductor substrate 210 is subsequently steppedlaterally relative to the extreme ultraviolet mask 205 c in operationS725. In operation S730, a distance between the semiconductor substrate210 and the extreme ultraviolet mask 205 c is changed so that thephotoresist layer 250 and the extreme ultraviolet mask 205 c areseparated by a second distance.

Then, in operation S735, the first portion of the photoresist layer 250is exposed to a second exposure dose of extreme ultraviolet radiationusing a second portion of the mask 205 c, and a second portion of thephotoresist layer 250 is exposed to the second exposure dose using thefirst portion of the mask 205 c. The first portion and second portion ofthe photoresist layer 250 are exposed substantially simultaneouslyduring the exposure operation. In some embodiments, the semiconductorsubstrate 210 is then laterally stepped relative to the mask 205 c inoperation S740. In operation S745, the distance between thesemiconductor substrate 210 and the mask 205 c is changed so that thephotoresist layer 250 and the mask 205 c are separated by a thirddistance. Then, in operation S750, the first portion of the photoresistlayer 250 is exposed to a third exposure dose of extreme ultravioletradiation using a third portion of the mask 205 c, the second portion ofthe photoresist layer 250 is exposed to the third exposure dose ofextreme ultraviolet radiation using the second portion of the mask 205c, and a third portion of the photoresist layer is exposed to the thirdexposure dose using the first portion of the mask 205 c. In someembodiments, the first, second, and third portions of the photoresistlayer 250 are exposed substantially simultaneously. In some embodiments,the semiconductor substrate 210 is then laterally stepped relative tothe mask 205 c in operation S755, and the distance between thesemiconductor substrate 210 and the mask 205 c is changed in operationS760, so that the photoresist layer 250 and the extreme ultraviolet mask205 c are separated by a fourth distance. Then, in operation S765, thefirst portion of the photoresist layer 250 is exposed to a fourthexposure dose of extreme ultraviolet radiation using a fourth portion ofthe mask 205 c, the second portion of the photoresist layer 250 isexposed to the fourth exposure dose of extreme ultraviolet radiationusing the third portion of the mask 205 c, a third portion of thephotoresist layer 250 is exposed to the fourth exposure dose using thesecond portion of the mask 205 c, and a fourth portion of thephotoresist layer 250 is exposed to the fourth exposure dose of extremeultraviolet radiation using the first portion of the mask 205 c. In someembodiments, the first, second, third, and fourth portions of thephotoresist layer 250 are exposed substantially simultaneously.

In some embodiments, the first portion of the mask 205 c, the secondportion of the mask 205 c, the third portion of the mask 205 c, and thefourth portion of the mask 205 c each have the same pattern. In someembodiments, the first distance is greater than the target distance, thesecond distance is less than the target distance, the third distance isgreater than the target distance, and the fourth distance is less thanthe target distance. In other embodiments, the first distance is lessthan the target distance, the second distance is greater than the targetdistance, the third distance is less than the target distance, and thefourth distance is greater than the target distance. In someembodiments, the distance between the photoresist layer 250 and the mask205 c is changed by raising or lowering the wafer stage 255. In someembodiments, a mean distance of the first distance, the second distance,the third distance, and the fourth distance is the target distance. Insome embodiments, a total of all the exposure doses received by eachportion of the photoresist layer 250 is equal to the target expose dose.

FIG. 11 is a flow chart illustrating a method 800 of manufacturing asemiconductor device according to an embodiment of the presentdisclosure. The sequential method includes an operation S810 of placinga semiconductor substrate 210 on a wafer stage 255. The semiconductorsubstrate 210 has a photoresist layer 250 disposed thereon. In operationS820, a first portion of the photoresist layer 250 is exposed to a firstexposure dose of extreme ultraviolet radiation using a first portion ofan extreme ultraviolet mask 205 c. The semiconductor substrate 210 isthen moved relative to the extreme ultraviolet mask 205 c in operationS830 followed by an operation S840 of exposing the first portion of thephotoresist layer 250 to a second exposure dose of extreme ultravioletradiation using a second portion of the mask 205 c, and exposing asecond portion of the photoresist layer 250 to the second exposure doseusing the first portion of the mask 205 c. The moving operation S830includes laterally stepping the mask 205 c so that the same portion ofthe mask 205 images a first die on the semiconductor substrate 210 in afirst exposure operation and then images a second, different die on thesemiconductor substrate 210 in a subsequent exposure operation, orchanging the distance between the mask 205 c and the photoresist layer250 by moving or tilting the wafer stage 255 in the vertical directionrelative to the mask in some embodiments. In some embodiments, the firstand second portions of the photoresist layer 250 are exposedsubstantially simultaneously by a scanning exposure during the exposureoperation S820.

Next, in operation S850 the semiconductor substrate 210 is movedrelative to the extreme ultraviolet mask 205 c. The moving operationS850 includes laterally stepping the mask 205 c or changing the distancebetween the mask 205 c and the photoresist layer 250 by moving ortilting the wafer stage 255 in the vertical direction relative to themask in some embodiments. Following the moving operation S850, the firstportion of the photoresist layer 250 is exposed to a third exposure doseof extreme ultraviolet radiation using a third portion of the mask 205c, the second portion of the photoresist layer 250 is exposed to thethird exposure dose of extreme ultraviolet radiation using the secondportion of the mask 205 c, and the third portion of the photoresistlayer 250 to is exposed to the third exposure dose using the firstportion of the mask 205 c in operation S860. In some embodiments, thefirst, second, and third portions of the photoresist layer 250 areexposed substantially simultaneously by a scanning exposure during theexposure operation S860.

Then, in operation S870 the semiconductor substrate 210 is movedrelative to the mask 205 c by laterally stepping or vertically movingthe wafer stage 255 followed by the operation S880 of exposing the firstportion of the photoresist layer 250 to a fourth exposure dose ofextreme ultraviolet radiation using a fourth portion of the mask 205 c,exposing the second portion of the photoresist layer 250 to the fourthexposure dose of extreme ultraviolet radiation using the third portionof the mask 205 c, exposing a third portion of the photoresist layer 250to the fourth exposure dose using the second portion of the mask 205 c,and exposing a fourth portion of the photoresist layer 250 to the fourthexposure dose of extreme ultraviolet radiation using the first portionof the mask 205 c. In some embodiments, the first, second, third, andfourth portions of the photoresist layer 250 are exposed substantiallysimultaneously by a scanning exposure during the exposure operation. Thefirst exposure dose, the second exposure dose, third exposure dose, andfourth exposure dose are each about one quarter of a target totalexposure dose.

In some embodiments, moving the semiconductor substrate 210 relative tothe mask 205 c includes stepping the semiconductor substrate 210 in alateral direction L relative to the mask 205 c. In some embodiments,moving the semiconductor substrate 210 relative to the mask 205 cincludes moving the semiconductor substrate 210 closer to or furtheraway from the mask 205 c in a vertical direction V. In some embodiments,moving the semiconductor substrate 210 relative to the mask 205 cincludes tilting the semiconductor substrate 210 relative to the mask205 c. In some embodiments, the mask 205 c is tilted an angle θ aboutthe X-axis. In some embodiments, the first portion of the mask 205 c,the second portion of the mask 205 c, the third portion of the mask 205c, and the fourth portion of the mask 205 c each have the same pattern.

FIG. 12 is a flow chart illustrating a method 900 of manufacturing asemiconductor device according to an embodiment of the presentdisclosure. The sequential method includes an operation S905 of dividingNax into p terms, where Nax is a number of dies along an x axis in a diematrix in each exposure field in an exposure field matrix to bedelineated on a semiconductor substrate and each of the p terms is atleast 1, wherein the x axis is parallel to one edge of a smallestrectangle enclosing the exposure field matrix, called the exposure fieldmatrix. In operation S910, Nay is divided into q terms, where Nay is anumber of dies along a y axis in the die matrix and each of the q termsis at least 1, wherein the y axis is perpendicular to the x axis. Then,a sequence SNx0 is formed by repeating Nbx+1 times the p terms in orderin operation S915. Nbx is an integer closest to Rx/Fx, where Rx is asize along the x axis of the exposure field matrix enclosure and Fx isan exposure field size along the x axis. In operation S920, a sequenceSNx1 is formed by eliminating first and last elements of SNx0, and asequence SNx is formed by multiplying each element of SNx1 by Dx inoperation S925, where Dx is a die size along the x axis. Next, asequence SNxr is formed by reversing an order of SNx in operation S930.

Then, a sequence SNy0 is formed by repeating Nby+1 times the q terms inorder in operation S935. Nby is an integer closest to Ry/Fy, where Ry isa size along the y axis of the exposure field matrix enclosure, and Fyis an exposure field size along the y axis. A sequence SNy1 is formed byeliminating first and last elements of SNy0 in operation S940. Inoperation S945, a sequence SNy is formed by multiplying each element ofSNy1 by Dy, where Dy is a die size along the y axis. Next, a sequenceSNyr is formed by reversing an order of SNy in operation S950.

Then, p*(Nbx+1)−2 stepping operations are performed in a third directionand first sequence exposure/stepping/exposure operations and secondsequence exposure/stepping/exposure operations are performed alternatelybetween any two adjacent stepping operations as well as before a firststepping operation and after a last stepping operation in operationS955. A distance of each stepping operation in order follows thesequence SNx.

As shown in S960, the first sequence exposure/stepping/exposureoperations include q*(Nby+1)−2 stepping operations in a first directionand one exposure operation between any two adjacent stepping operationsas well as before the first stepping operation and after the laststepping operation, and the distance of each stepping operation in orderfollows the sequence SNy. The first exposure operation in the firstsequence exposure/stepping/exposure operations exposes Nax_1*Nay_1 diesin a corner of an exposure field in a corner of the exposure fieldmatrix enclosure.

As shown in S965, the second sequence exposure/stepping/exposureoperations include q*(Nby+1)−2 stepping operations in a second directionand one exposure operation between any two adjacent stepping operationsas well as before the first stepping operation and after the laststepping operation, and the distance of each stepping operation in orderfollows the sequence SNyr.

In some embodiments, the focus settings of all exposure operations inorder alternate between Fo−dF and Fo+dF, where Fo is an optimum focusposition, Fo−dF is a focus position above the optimum focus position Fo,and Fo+dF is a focus position below the optimum focus position Fo.

In some embodiments, a total exposure dose accumulated in each die iswithin 0.9*Eo to 1.1*Eo, where Eo is an optimum exposure dose.

In some embodiments, the method includes skipping exposure operationsfor missing exposure fields in the exposure field matrix enclosure.

In some embodiments, the method includes merging stepping operationsfrom after a previous exposure operation to before a subsequent exposureoperation into one stepping operation which moves directly from aprevious exposure location to a subsequent exposure location. As shownin FIG. 13, the wafer stage is directly moved from a previous exposurelocation so that the mask 205 c″ is positioned over a subsequentexposure location, thereby skipping exposure operations where there isno die to be exposed resulting from missing exposure fields in theexposure field matrix enclosure.

In some embodiments, both the exposure field corner and the exposurefield matrix enclosure corner are lower left corners as viewed in planview, the first direction is in the +y direction, the second directionis in the −y direction, and the third direction is in the +x direction.

In some embodiments, both the exposure field corner and the exposurefield matrix enclosure corner are upper left corners as viewed in planview, the first direction is in the −y direction, the second directionis in the +y direction, and the third direction is in the +x direction.

In some embodiments, both the exposure field corner and the exposurefield matrix enclosure corner are lower right corners as viewed in planview, the first direction is in the +y direction, the second directionis in the −y direction, and the third direction is in the −x direction.

In some embodiments, both the exposure field corner and the exposurefield matrix enclosure corner are upper right corners as viewed in planview, the first direction is in the −y direction, the second directionis in the +y direction, and the third direction is in the −x direction.

FIG. 14 is a flow chart illustrating a method 1000 of manufacturing asemiconductor device according to an embodiment of the presentdisclosure. The sequential method includes an operation S1005 ofdividing Nax into p terms, where Nax is a number of dies along an x axisin a die matrix in each exposure field in an exposure field matrix to bedelineated on a semiconductor substrate and each of the p terms is atleast 1, wherein the x axis is parallel to one edge of a smallestrectangle enclosing the exposure field matrix, called the exposure fieldmatrix. In operation S1010, Nay is divided into q terms, where Nay is anumber of dies along a y axis in the die matrix and each of the q termsis at least 1, wherein the y axis is perpendicular to the x axis. Then,a sequence SNx0 is formed by repeating Nbx+1 times the p terms in orderin operation S1015. Nbx is an integer closest to Rx/Fx, where Rx is asize along the x axis of the exposure field matrix enclosure and Fx isan exposure field size along the x axis. In operation S1020, a sequenceSNx1 is formed by eliminating first and last elements of SNx0, and asequence SNx is formed by multiplying each element of SNx1 by Dx inoperation S1025, where Dx is a die size along the x axis. Next, asequence SNxr is formed by reversing an order of SNx in operation S1030.

Then, a sequence SNy0 is formed by repeating Nby+1 times the q terms inorder in operation S1035. Nby is an integer closest to Ry/Fy, where Ryis a size along the y axis of the exposure field matrix enclosure, andFy is an exposure field size along the y axis. A sequence SNy1 is formedby eliminating first and last elements of SNy0 in operation S1040. Inoperation S1045, a sequence SNy is formed by multiplying each element ofSNy1 by Dy, where Dy is a die size along the y axis. Next, a sequenceSNyr is formed by reversing an order of SNy in operation S1050.

Then, q*(Nby+1)−2 stepping operations are performed in a third directionand first sequence exposure/stepping/exposure operations and secondsequence exposure/stepping/exposure operations are performed alternatelybetween any two adjacent stepping operations as well as before a firststepping operation and after a last stepping operation in operationS1055. A distance of each stepping operation in order follows thesequence SNy.

As shown in S1060, the first sequence exposure/stepping/exposureoperations include p*(Nbx+1)−2 stepping operations in a first directionand one exposure operation between any two adjacent stepping operationsas well as before the first stepping operation and after the laststepping operation, and the distance of each stepping operation in orderfollows the sequence SNx. The first exposure operation in the firstsequence exposure/stepping/exposure operations exposes Nax_1*Nay_1 diesin a corner of an exposure field in a corner of the exposure fieldmatrix enclosure.

As shown in S1065, the second sequence exposure/stepping/exposureoperations include p*(Nbx+1)−2 stepping operations in a second directionand one exposure operation between any two adjacent stepping operationsas well as before the first stepping operation and after the laststepping operation, and the distance of each stepping operation in orderfollows the sequence SNxr.

FIGS. 15-49 show a method of exposing a photoresist-coated semiconductorwafer 210 according to an embodiment of the present disclosure. As shownin FIG. 15, a lower left side die is first exposed to radiation at afocus position above a target focus. In this embodiment, a numberindicates the total number of accumulated exposures in this die; anegative sign (−) indicates in this die there is an unpaired exposuredone at a focus position above the target focus; a positive sign (+)indicates in this die there is an unpaired exposure done at a focusposition below the target focus.

The mask 205 c is subsequently moved up relative to the wafer 210 inFIG. 16, and three dies are exposed at a focus position below the targetfocus. Thus, the originally exposed die (lower left die) has beenexposed twice, once above the target focus and once below the targetfocus, resulting in two exposures at the first die. The two dies abovethe first die have each been exposed once at a focus position below thetarget focus.

The mask 205 c is shown as having six pattern areas having the samepattern, and thus up to six dies can be exposed at once. However, thepresent disclosure is not limited to masks having six of the samepattern, and in some embodiments, the mask contains two, three, four,five, or more than six of the same pattern enabling two, three, four,five, or more dies on the wafer to be imaged at the same time.

In FIG. 17, the mask 205 c is moved up relative to the wafer 210 and thewafer 210 is exposed at a focus position above the target focus. Asexplained herein, moving the mask 205 c relative to the wafer 210 isaccomplished by moving the wafer stage 255 in some embodiments.

As shown in FIG. 18, the mask 205 c is moved up relative to the wafer210 and an exposure below the target focus is performed. The twouppermost dies have been exposed once, and the four lower dies have beenexposed twice.

As shown in FIG. 19, the mask 205 c is moved up relative to the wafer210 and the two upper lower left side dies are exposed a second time ata focus position below the target focus. Thus, each die in the left sidefirst column of dies have been exposed twice.

The mask 205 c is subsequently moved to the right relative to the wafer210 in FIG. 20, and four dies are exposed at a focus position below thetarget focus. Thus, the two uppermost dies in the first column have beenexposed three times, once above the target focus and twice below thetarget focus, and the two uppermost dies in the second column have eachbeen exposed once at a focus position below the target focus.

In FIG. 21, the mask 205 c is moved down relative to the wafer 210 andthe wafer 210 is exposed at a focus position above the target focus.Thus, the two uppermost dies in the first column have been exposed fourtimes, and the two uppermost dies in the second column have been exposedtwice. The third dies from the top in the first and second columns havebeen exposed three times and once, respectively.

As shown in FIG. 22, the mask 205 c is moved down relative to the wafer210 and an exposure below the target focus is performed. The third diefrom the top of first column has now been exposed four times, the thirddie from the top of the second column has been exposed twice, the secondand third dies from the bottom of the first column have been exposedthree times, and the second and third dies from the bottom of the secondcolumn have been exposed once.

The mask 205 c is subsequently moved to down relative to the wafer 210in FIG. 23, and the three lower dies in both the first and secondcolumns are exposed at a focus position above the target focus. Thus,the second and third dies from bottom of the first column have beenexposed four times. The second and third dies from bottom of the secondcolumns have been exposed twice. The bottom die in first column has beenexposed three times, and the bottom die in the second column has beenexposed once.

In FIG. 24, the mask 205 c is moved down relative to the wafer 210 andthe wafer 210 is exposed at a focus position below the target focus.After this step, all the dies in the first column have been exposed fourtimes and all the dies in the second column have been exposed twice. Inembodiments where each exposure is about one-fourth of the totalexposure dose, each die in the first column is now fully exposed.

As shown in FIG. 25, the mask 205 c is moved to the right relative tothe wafer 210 and an exposure above the target focus is performed. Thebottom die in the second column has now been exposed three times, andthe bottom die in the third column has been exposed once.

The mask 205 c is subsequently moved up relative to the wafer 210 inFIG. 26, and six dies are exposed at a focus position below the targetfocus. Thus, the second and third dies from the bottom of the secondcolumn have been exposed three times, once above the target focus andtwice below the target focus, and the second and third dies from thebottom of the third column have been exposed once. The bottom dies ofthe second and third columns have been exposed four times and twice,respectively.

In FIG. 27, the mask 205 c is moved up relative to the wafer 210 and thewafer 210 is exposed at a focus position above the target focus. Thus,the second and third dies from the bottom of the second column have beenexposed four times, and the third die from the top of the second columnhas been exposed three times. The second and third dies from the bottomof the third have been exposed twice, and the third die from the top ofthe third column has been exposed once.

As shown in FIG. 28, the mask 205 c is moved up relative to the wafer210 and an exposure below the target focus is performed. The twouppermost dies in the second column are exposed a third time, and thethird die from the top of second column has now been exposed four times.The two uppermost dies in the third column have been exposed once, andthe third die from the top of the third column has been exposed twice.

The mask 205 c is subsequently moved up relative to the wafer 210 inFIG. 29, and the two uppermost dies in the second and third columns areexposed at a focus position above the target focus. Thus, the twouppermost dies in the second column have been exposed four times, andthe two uppermost dies in the third column have been exposed twice.

In FIG. 30, the mask 205 c is moved to the right relative to the wafer210 and the wafer 210 is exposed at a focus position below the targetfocus. Thus, the two uppermost dies in the third column and the twouppermost dies in the fourth column have been exposed three times andonce, respectively.

As shown in FIG. 31, the mask 205 c is subsequently moved down relativeto the wafer 210 and an exposure above the target focus is performed.The two uppermost dies in the third and fourth column have now beenexposed four and two times, respectively. The third die from the top ofthe third column has been exposed three times, and the third die fromthe top of the fourth column has been exposed once.

As shown in FIG. 32, the mask 205 c is moved down relative to the wafer210 and six dies are exposed at a focus position below the target focus.Thus, the third dies from the top of the third and fourth columns havebeen exposed four and two times, respectively. The second and third diesfrom the bottom of the third column have been exposed three times. Thesecond and third dies from the bottom of the fourth column have beenexposed once.

The mask 205 c is subsequently moved down relative to the wafer 210 inFIG. 33, and six dies are exposed at a focus position above the targetfocus. Thus, the second and third dies from the bottom of the thirdcolumn have been exposed four times. The second and third dies from thebottom of the fourth column have been exposed twice. The bottom dies ofthe third and fourth columns have been exposed three times and once,respectively.

In FIG. 34, the mask 205 c is moved down relative to the wafer 210 andthe wafer 210 is exposed at a focus position below the target focus.Thus, the bottom dies in the third and fourth column have been exposedfour times and twice, respectively.

As shown in FIG. 35, the mask 205 c is moved to the right relative tothe wafer 210 and an exposure above the target focus is performed. Thebottom dies of the fourth and fifth columns have now been exposed threetimes and once, respectively.

The mask 205 c is subsequently moved up relative to the wafer 210 inFIG. 36, and the six lower dies in the fourth and fifth columns areexposed at a focus position below the target focus. Thus, the second andthird dies from bottom of the fourth column have been exposed threetimes. The second and third dies from bottom of the fifth column havebeen exposed once. The bottom die in fourth column has been exposed fourtimes, and the bottom die in the fifth column has been exposed twice.

In FIG. 37, the mask 205 c is moved up relative to the wafer 210 and thewafer 210 is exposed at a focus position above the target focus. Thesecond and third dies from the bottom of the fourth column have now beenexposed four times and the second and third dies from the bottom of thefifth column have been exposed twice. The third die from the top of thefourth column has been exposed three times and the third die from thetop of the fifth column has been exposed once.

As shown in FIG. 38, the mask 205 c is moved up relative to the wafer210 and an exposure below the target focus is performed. The twouppermost dies in the fourth column have now been exposed three times,and the two uppermost dies in the fifth column have been exposed once.The third die from the top of the fourth column has been exposed fourtimes and the third die from the top of the fifth column has beenexposed twice.

In FIG. 39, the mask 205 c is moved up relative to the wafer 210 andfour dies are exposed at a focus position above the target focus. Thetwo uppermost dies of the fourth column have been exposed four times,and the two uppermost dies of the fifth column have been exposed twice.

As shown in FIG. 40, the mask 205 c is moved to the right relative tothe wafer 210 and an exposure below the target focus is performed. Thetwo uppermost dies in the fifth column are exposed a third time, and thetwo uppermost dies in the fifth column have been exposed once.

The mask 205 c is subsequently moved down relative to the wafer 210 inFIG. 41, and the six dies in the upper right corner of the fifth andsixth columns are exposed at a focus position above the target focus.Thus, the two uppermost dies in the fourth column have been exposed fourtimes, and the two uppermost dies in the sixth column have been exposedtwice. The third die from the top of the fifth column has been exposedthree times and the third die from the top of the sixth column has beenexposed once.

In FIG. 42, the mask 205 c is moved down right relative to the wafer 210and the wafer 210 is exposed at a focus position below the target focus.Thus, the second and third dies from the bottom of the fifth column andthe second and third dies from the bottom of the have been exposed threetimes and once, respectively. The third die from the top of the fifthcolumn and third die from the top of the sixth column have been exposedfour times and twice, respectively.

As shown in FIG. 43, the mask 205 c is subsequently moved down relativeto the wafer 210 and an exposure above the target focus is performed.The second and third dies from the bottom of fifth and sixth columnshave now been exposed four and two times, respectively. The bottom diesof the fifth and sixth columns have been exposed three times and once,respectively.

As shown in FIG. 44, the mask 205 c is moved down relative to the wafer210 and an exposure below the target focus is performed. The two bottomdies in the fifth and sixth columns have now been exposed four times andtwice, respectively.

The mask 205 c is subsequently moved to the right relative to the wafer210 in FIG. 45, and the bottom die in the sixth column is exposed at afocus position above the target focus. Thus, the bottom die of the sixthcolumn has been exposed three times.

In FIG. 46, the mask 205 c is moved up relative to the wafer 210 andfour dies are exposed at a focus position below the target focus. Thebottom die in the sixth column has now been exposed four times, and thesecond and third dies from the bottom of the sixth column have beenexposed three times.

As shown in FIG. 47, the mask 205 c is moved up relative to the wafer210 and an exposure above the target focus is performed. The second andthird dies from the bottom of the sixth column have been exposed fourtimes and the third die from the top of the sixth column has beenexposed once.

The mask 205 c is subsequently moved up relative to the wafer 210 inFIG. 48, and an exposure below the target focus is performed. The twouppermost dies in the sixth column have now been exposed three times,and the third die from the top of the sixth column has been exposed fourtimes.

In FIG. 49, the mask 205 c is moved up relative to the wafer 210 and thewafer 210 is exposed at a focus position above the target focus. The twouppermost dies of the sixth column have been exposed four times, thus,all the dies in the 6×6 array have been exposed four times.

The 6×6 array of dies on the semiconductor wafer 210 or the 2×3 array ofdies in one mask of FIGS. 15-49 are examples of the disclosure and thepresent disclosure is not limited to a wafer with 36 dies or a mask with6 identical die patterns. In some embodiments, fewer than 36 dies ormore than 36 dies are exposed. In the embodiment of FIGS. 15-49, themask 205 c was moved or stepped relative to the wafer 210 in a cycle ofstepping from one die to an adjacent die, then stepping two dies away,followed by stepping to an adjacent die, and alternating between aone-die step and a two-die step.

In some embodiments, a 3×8 array of dies on the photoresist-coatedsemiconductor wafer 210 are exposed to radiation using a mask 205 c′having a 1×4 array of mask areas on the mask, corresponding to a 1×4exposure field, as shown in FIGS. 50-53. The four mask areas all havethe same pattern.

As shown in FIG. 50, a lower left side die is first exposed using afirst mask area.

The mask 205 c′ is subsequently moved up relative to the wafer 210 inFIG. 51, and a second die is exposed using the first mask area and thefirst die is exposed using a second mask area.

In FIG. 52, the mask 205 c′ is moved up relative to the wafer 210 and athird die is exposed using the first mask area, the second die isexposed using the second mask area, and the first die is exposed using athird mask area. As explained herein, moving the mask 205 c′ relative tothe wafer 210 is accomplished by moving the wafer stage 255 in someembodiments.

As shown in FIG. 53, the mask 205 c′ is moved up relative to the wafer210, and a fourth die is exposed using the first mask area, the thirddie is exposed using the second mask area, the second die is exposedusing the third mask area, and the first mask area. The stepping andexposure operations are repeated, stepping the mask 205 c′ relative tothe wafer 210 one die at a time until all the dies in a column areexposed the same number of times. Then, the mask is stepped one die tothe right relative to the wafer and a second column of dies are exposedin a similar manner as the first column. The stepping and exposureoperations are repeated until all the dies are exposed the same numberof times.

In some embodiments, the array of dies on the photoresist-coatedsemiconductor wafer 210 is not a rectangular, but rather is made of upof series rectangular exposure fields arranged in manner to make moreefficient use of the circular area of a wafer. In an embodiment, aplurality of rectangular exposure fields are arranged, as shown in FIGS.54-110. In particular, a column-wise 2×3 folding exposure (where p=2 andq=3) for an embodiment having a die matrix of Nax=3 and Nay=6 isillustrated.

As shown in FIG. 54, the number of dies along the x axis of an exposurefield is 3 and the number of dies along they axis of the exposure fieldis 6. Dx is the die size along the x axis and Dy is the die size alongthe y axis. Rx is a size along the x axis of the exposure field matrixenclosure and Fx is an exposure field size along the x axis. Ry is asize along the y axis of the exposure field matrix enclosure and Fy isan exposure field size along the y axis.

In some embodiments, the matrix of dies on the photoresist-coatedsemiconductor substrate 210 is exposed to radiation using a mask 205 c″having a 3×6 array of mask areas on the mask, corresponding to a 3×6exposure field, as shown in FIGS. 55-110. The eighteen mask areas allhave the same pattern.

As shown in FIG. 55, the right side column of the mask 205 c″ is alignedwith the left side column of a dies and a top row of the mask 205 c″ isaligned with a bottom row of dies. In FIG. 56, the mask 205 c″ isstepped up two die widths relative to the semiconductor substrate 210and no exposure is performed because the mask 205 c″ is not positionedover a portion of the wafer to be exposed. Next, the mask 205 c″ isstepped up three die widths relative to the semiconductor substrate, asshown in FIG. 57 so that an edge of the mask 205 c″ is adjacent edge ofa lower left corner of an exposure field. The mask is subsequentlystepped up one die relative to the wafer 210 and the first die in theleft side column is exposed to radiation in FIG. 58 using the upper maskarea in the right side column of mask 205 c″. The exposure (0) is belowa target focus position (+).

The mask 205 c″ is subsequently stepped up two die widths relative tothe wafer 210 in FIG. 59, and the third die from the bottom of the leftside column, the second die, and the first die are exposed using thefirst, second, and third mask areas from the top of the mask 205 c″,respectively. The exposure (1) is above a target focus position (−).

Then in FIG. 60, the mask 205 c″ is stepped up three die widths relativeto the wafer and the six dies in the left most column of the exposurefield are exposed using the six mask areas in the right column of themask 205 c″. In this embodiment, the numbers indicate to which shotseach die are exposed. Where “0” is the first shot, “1” is the secondshot, “2” is the third shot, and so on. A negative sign (−) indicates inthis die there is an unpaired exposure done at a focus position abovethe target focus; a positive sign (+) indicates in this die there is anunpaired exposure done at a focus position below the target focus, and apair of (−) and (+) indicates this die has a pair of exposure doses at afocus position above and below the target focus. An odd number of (−)and (+) indicates the total exposure dose is unpaired. An even number of(−) and (+) indicates the total exposure dose is paired.

The mask 205 c″ is then stepped up one die width relative to the wafer210 in FIG. 61, and the first through fifth dies from the top of theleft side (first) column are exposed (3) at a focus position above thetarget focus (−) using the second through sixth mask areas from the topof the right side of the mask.

As shown in FIG. 62, the mask 205 c″ is stepped up two die widthsrelative to the wafer 210, and the first through third dies from the topof the first column are exposed using the fourth through sixth maskareas, the fifth die is exposed using the second mask area, the fourthdie is exposed using the third mask area in the right column of themask. The focus position of this exposure (4) is below the target focusposition (+).

Next, the mask 205 c″ is stepped two die widths to the right, as shownin FIG. 63, and the top three rows of dies in the exposure field areexposed using the bottom three rows of the mask. The focus position ofthis exposure (5) is above the target focus position (−).

As shown in FIG. 64, the mask 205 c″ is moved down two die widthsrelative to the wafer 210, and the top five rows of dies in the exposurefield are exposed using the bottom five rows of the mask. The focusposition of this exposure (6) is below the target focus (+).

Next, as shown in FIG. 65, the mask 205 c″ is stepped down one die widthand the all three columns and six rows of the mask are used to exposethe left side exposure field of the wafer. The focus position of thisexposure (7) is above the target focus (−).

In FIG. 66, the mask 205 c″ is stepped down three die widths relative tothe wafer and the bottom three rows of the left exposure field areexposed using the upper three rows of the mask. The focus position ofthis exposure (8) is below the target focus (+).

Next, in FIG. 67, the mask 205 c″ is stepped down two die widthsrelative to the wafer and the bottom row of the left exposure field isexposed using the upper row of the mask. The focus position of thisexposure (9) is above the target focus (−).

Then, in FIG. 68, the mask 205 c″ is stepped down one die width. Anexposure is not performed because the mask is not positioned over aportion of the wafer to be exposed. The mask 205 c″ is subsequentlystepped down two widths in successive steps, as shown in FIGS. 69 and70. The upper row of the mask is aligned with and adjacent to the bottomrow of the array of dies. No exposures are performed after either ofthese stepping operations.

Then, in FIG. 71, the mask 205 c″ is stepped one die width to the rightand the die at the bottom left corner of the exposure field is exposed.The focus position of this exposure (a) is above the target focus (−).In FIGS. 71 to 96, the shot numbers will be designated by successiveletters (a-z) because all the single digit numbers have been used.

As shown in FIGS. 72, 73, 74, 75, 76, 77, and 78, an alternatingsequence of below focus position and above focus position exposures,combined with an alternating sequence of the two die width step up,three die width step up, and one die width step up is performed.

Then, the mask 205 c″ is stepped two die widths to the right, as shownin FIG. 79, and the top three rows of middle exposure field are exposed.This exposure (i) is above the target focus position (−). Then, as shownin FIGS. 80, 81, 82, 83, 84, 85, and 86, an alternating sequence ofbelow focus position and above focus position exposures, combined withan alternating sequence of the two die width step down, three die widthstep down, and one die width step down is performed. The mask 205 c″ issubsequently stepped one die width to the right relative to thesemiconductor substrate 210, as shown in FIG. 87, and an exposure isperformed. This exposure (q) is above the target focus position (−).

As shown in FIGS. 88, 89, 90, 91, 92, 93, and 94, the alternatingsequence of above focus position and below focus position exposures,combined with the alternating sequence of the two die width step up,three die width step up, and one die width step up are performed. Then,the mask 205 c″ is stepped two die widths to the right and the threeuppermost rows of dies in the three leftmost columns are exposed (y) ata focus position above the target focus, as shown in FIG. 95.

Then, as shown in FIGS. 96, 97, 98, and 99, an alternating sequence ofbelow focus position and above focus position exposures, combined withan alternating sequence of the two die width step down, three die widthstep down, and one die width step down is performed. The mask 205 c″ issubsequently stepped one die width down relative to the wafer 210 to beadjacent to the bottom row of the three leftmost columns of dies asshown in FIG. 100. No exposure is performed because the mask is notpositioned over a portion of the wafer to be exposed. Starting with theexposure in FIG. 97, Greek letters are used to designate the shotnumbers, as the English alphabet letters have all been used.

In FIGS. 101 and 102 the mask is stepped downward relative to the wafer210 three and two die widths, respectively, and no exposures areperformed after the stepping operations. Then, the masked is stepped onedie width to the right relative to the wafer 210 in FIG. 103. The mask205 c″ is then stepped up relative to wafer 210 to the right relative tothe semiconductor substrate 210, in two stepping operations of two diewidths and three die widths, respectively, as shown in FIGS. 104 and105, to be adjacent the two rightmost bottom row dies of the rightmostexposure field.

Next, the mask 205 c″ is stepped one die width in the up direction andan exposure (δ) is performed below the target position (+), as shown inFIG. 106. As shown in FIGS. 107, 108, 109, and 110 the alternatingsequence of above focus position and below focus position exposures,combined with the alternating sequence of the two die width step up,three die width step up, and one die width step up are performed.

In this embodiment, the stepping operations alternated between two diewidth, three die width, and one die width steps between exposures whenthe mask was moving relative to the wafer along the y axis, and steppingoperations alternated between two die width and one die width stepsbetween exposures when the mask was moving relative to the wafer alongthe x axis. The alternating sequence of above focus position and belowfocus position exposures, combined with the alternating sequences ofstepping was performed until all the dies were exposed a same number oftimes, and all the above focus position exposures are each paired with abelow focus position exposures.

In some embodiments, each die is exposed six times. In otherembodiments, the exposure/stepping/exposure operations are arranged sothat each die is exposed four times or eight times. In some embodiments,the total accumulated exposure dose each die receives is within about75% to about 125% of a target exposure dose.

The present disclosure is not limited to the embodiments disclosed, andadditional die matrix and mask arrangements are evident to one of skillin the art in view of this disclosure. Further, additional steppingsequences are evident to one of skill in this art in view of thisdisclosure.

In some embodiments, exposures at the target focus position areperformed in addition to exposures above the target focus position andbelow the target focus position.

In some embodiments, a method of inspecting a photomask is provided. Themethod includes inspecting a mask including a plurality of the samecircuit patterns. The mask is inspected. If a defect is found at aspecific location of one of the circuit patterns and not found at thesame locations in other same circuit patterns on the mask the maskpasses the inspection. If a defect is found in one mask pattern it willnot be resolved in the imaged photoresist in some embodiments.

In some embodiments, a mask having a plurality of the same circuitpatterns is provided. One of the plurality of the same circuit patternshas a defect at a specific location. The other same circuit patterns donot have the same defect at the same location. The mask is acceptablefor use in a photolithography process in some embodiments because thedefect on only one of the plurality of same circuit patterns will not beresolved in the imaged photoresist exposed using the mask with thedefect.

Although performing the multiple exposures at different focus positionsmay increase the time it takes to expose all the dies on the wafer, theoverall semiconductor device manufacturing method is more efficientbecause of the decrease in defects and increased device yield providedby embodiments of the disclosure. Multiple exposures of the same portionof a photoresist layer by different portions of a mask having the samecircuit pattern prevents defects or contaminant particles formed on asingle mask pattern from adversely affecting the pattern formed in thephotoresist layer using the mask with the defect or particulatecontamination. In addition, performing multiple exposures of the sameportion of a photoresist layer at different focus positions above andbelow the target focus improves the pattern resolution over the heightof the pattern feature from the pattern feature base to the uppersurface of the pattern feature. Performing the methods of the presentdisclosure provides improved image log slope (ILS) and improved maskerror enhancement factor (MEEF).

An embodiment of the disclosure is a method of manufacturing asemiconductor device, includes coating a photoresist layer on asemiconductor substrate. A target total exposure dose is determined forthe photoresist layer. A target focus position is determined for thephotoresist layer. A first portion of the photoresist layer is exposedto a first exposure dose of extreme ultraviolet radiation at a firstfocus position using a first portion of an extreme ultraviolet mask. Thesemiconductor substrate is moved a first time relative to the extremeultraviolet mask. The first portion of the photoresist layer is exposedto a second exposure dose of extreme ultraviolet radiation using asecond portion of the mask at a second focus position, and a secondportion of the photoresist layer is exposed to the second exposure doseat the second focus position using the first portion of the extremeultraviolet mask. In an embodiment, the method includes moving thesemiconductor substrate a second time relative to the mask, and exposingthe first portion of the photoresist layer to a third exposure dose ofextreme ultraviolet radiation at a third focus position using a thirdportion of the mask, exposing the second portion of the photoresistlayer to the third exposure dose of extreme ultraviolet radiation at thethird focus position using the second portion of the mask, and exposinga third portion of the photoresist layer to the third exposure dose atthe third focus position using the first portion of the mask. In anembodiment, the method includes moving the semiconductor substrate afourth time relative to the mask, and exposing the first portion of thephotoresist layer to a fourth exposure dose of extreme ultravioletradiation at a fourth focus position using a fourth portion of the mask,exposing the second portion of the photoresist layer to the fourthexposure dose of extreme ultraviolet radiation at the fourth focusposition using the third portion of the mask, exposing a third portionof the photoresist layer to the fourth exposure dose at the fourth focusposition using the second portion of the mask, and exposing a fourthportion of the photoresist layer to the fourth exposure dose of extremeultraviolet radiation at the fourth focus position using the firstportion of the mask. In an embodiment, the first portion of the mask,the second portion of the mask, the third portion of the mask, and thefourth portion of the mask each have a same pattern. In an embodiment,the first exposure dose, the second exposure dose, the third exposuredose, and the fourth exposure dose are different. In an embodiment, thefirst exposure dose and the third exposure dose are same, and the secondexposure dose and the fourth exposure dose are same. In an embodiment,the first focus position is above the target focus position, the secondfocus position is below the target focus position, the third focusposition is above the target focus position, and the fourth focusposition is below the target focus position. In an embodiment, each ofthe first exposure dose, the second exposure dose, the third exposuredose, and the fourth exposure dose is less than the target exposuredose. In an embodiment, the method includes performing additionalexposure steps such that each portion of the photoresist layer isexposed a same number of times. In an embodiment, a total of all theexposure doses received by each portion of the photoresist layer isequal to the target exposure dose. In an embodiment, the focus positionalternates between above the target focus position and below the targetfocus position.

Another embodiment of the disclosure is a method of manufacturing asemiconductor device, including dividing Nax into p terms, where Nax isa number of dies along an x axis in a die matrix in each exposure fieldin an exposure field matrix to be delineated on a semiconductorsubstrate and each of the p terms is at least 1, wherein the x axis isparallel to one edge of a smallest rectangle enclosing the exposurefield matrix, called the exposure field matrix enclosure. Nay is dividedinto q terms, where Nay is a number of dies along a y axis in the diematrix and each of the q terms is at least 1, wherein the y axis isperpendicular to the x axis. A sequence SNx0 is formed by repeatingNbx+1 times the p terms in order, where Nbx is an integer closest toRx/Fx, where Rx is a size along the x axis of the exposure field matrixenclosure and Fx is an exposure field size along the x axis. A sequenceSNx1 is formed by eliminating first and last elements of SNx0, and asequence SNx is formed by multiplying each element of SNx1 by Dx, whereDx is a die size along the x axis. A sequence SNxr is formed byreversing an order of SNx. A sequence SNy0 is formed by repeating Nby+1times the q terms in order, where Nby is an integer closest to Ry/Fy,where Ry is a size along the y axis of the exposure field matrixenclosure and Fy is an exposure field size along the y axis. A sequenceSNy1 is formed by eliminating first and last elements of SNy0. Asequence SNy is formed by multiplying each element of SNy1 by Dy, whereDy is a die size along the y axis. A sequence SNyr is formed byreversing an order of SNy. p*(Nbx+1)−2 stepping operations are performedin a third direction and first sequence exposure/stepping/exposureoperations and second sequence exposure/stepping/exposure operations areperformed alternately between any two adjacent stepping operations aswell as before a first stepping operation and after a last steppingoperation. A distance of each stepping operation in order follows thesequence SNx. The first sequence exposure/stepping/exposure operationsinclude q*(Nby+1)−2 stepping operations in a first direction and oneexposure operation between any two adjacent stepping operations as wellas before a first stepping operation and after a last steppingoperation, where the distance of each stepping operation in orderfollows the sequence SNy. The first exposure operation in the firstsequence exposure/stepping/exposure operations exposes Nax_1*Nay_1 diesin a corner of an exposure field in a corner of the exposure fieldmatrix enclosure. The second sequence exposure/stepping/exposureoperations include q*(Nby+1)−2 stepping operations in a second directionand one exposure operation between any two adjacent stepping operationsas well as before a first stepping operation and after a last steppingoperation. The distance of each stepping operation in order follows thesequence SNyr. In an embodiment, focus settings of all exposureoperations in order alternate between Fo−dF and Fo+dF, where Fo is anoptimum focus position, Fo−dF is a focus position above the optimumfocus position, and Fo+dF is a focus position below the optimum focusposition. In an embodiment, a total exposure dose accumulated in eachdie is within 0.9*Eo to 1.1*Eo, where Eo is an optimum exposure dose. Inan embodiment, the method includes skipping exposure operations formissing exposure fields in the exposure field matrix enclosure. In anembodiment, the method includes merging stepping operations from after aprevious exposure operation to before a subsequent exposure operationinto one stepping operation which moves directly from a previousexposure location to a subsequent exposure location. In an embodiment,both the exposure field corner and the exposure field matrix enclosurecorner are lower left corners as viewed in plan view, the firstdirection is in the +y direction, the second direction is in the −ydirection, and the third direction is in the +x direction. In anembodiment, both the exposure field corner and the exposure field matrixenclosure corner are upper left corners as viewed in plan view, thefirst direction is in the −y direction, the second direction is in the+y direction, and the third direction is in the +x direction. In anembodiment, both the exposure field corner and the exposure field matrixenclosure corner are lower right corners as viewed in plan view, thefirst direction is in the +y direction, the second direction is in the−y direction, and the third direction is in the −x direction. In anembodiment, both the exposure field corner and the exposure field matrixenclosure corner are upper right corners as viewed in plan view, thefirst direction is in the −y direction, the second direction is in the+y direction, and the third direction is in the −x direction.

Another embodiment of the disclosure is a method of manufacturing asemiconductor device including dividing Nax into p terms, where Nax is anumber of dies along an x axis in a die matrix in each exposure field inan exposure field matrix to be delineated on a semiconductor substrateand each of the p terms is at least 1, wherein the x axis is parallel toone edge of a smallest rectangle enclosing the exposure field matrix,called the exposure field matrix enclosure. Nay is divided into q terms,where Nay is a number of dies along a y axis in the die matrix and eachof the q terms is at least 1, wherein the y axis is perpendicular to thex axis. A sequence SNx0 is formed by repeating Nbx+1 times the p termsin order, where Nbx is an integer closest to Rx/Fx, where Rx is a sizealong the x axis of the exposure field matrix enclosure and Fx is anexposure field size along the x axis. A sequence SNx1 is formed byeliminating first and last elements of SNx0. A sequence SNx is formed bymultiplying each element of SNx1 by Dx, where Dx is a die size along thex axis, and a sequence SNxr is formed by reversing an order of SNx. Asequence SNy0 is formed by repeating Nby+1 times the q terms in order,where Nby is an integer closest to Ry/Fy, where Ry is a size along the yaxis of the exposure field matrix enclosure and Fy is an exposure fieldsize along the y axis. A sequence SNy1 is formed by eliminating firstand last elements of SNy0. A sequence SNy is formed by multiplying eachelement of SNy1 by Dy, where Dy is a die size along the y axis. Asequence SNyr is formed by reversing an order of SNy. q*(Nby+1)−2stepping operations are performed in a third direction and firstsequence exposure/stepping/exposure operations and second sequenceexposure/stepping/exposure operations are performed alternately betweenany two adjacent stepping operations as well as before a first steppingoperation and after a last stepping operation. The distance of eachstepping operation in order follows the sequence SNy. The first sequenceexposure/stepping/exposure operations include p*(Nbx+1)−2 steppingoperations in a first direction and one exposure operation between anytwo adjacent stepping operations as well as before a first steppingoperation and after a last stepping operation, where a distance of eachstepping operation in order follows the sequence SNx. The first exposureoperation in the first sequence exposure/stepping/exposure operationsexposes Nax_1*Nay_1 dies in a corner of an exposure field in a corner ofthe exposure field matrix enclosure. The second sequenceexposure/stepping/exposure operations include p*(Nbx+1)−2 steppingoperations in a second direction and one exposure operation between anytwo adjacent stepping operations as well as before a first steppingoperation and after a last stepping operation. A distance of eachstepping operation in order follows the sequence SNxr. In an embodiment,focus settings of all exposure operations in order alternate betweenFo−dF and Fo+dF, where Fo is an optimum focus position, Fo−dF is a focusposition above the optimum focus position, and Fo+dF is a focus positionbelow the optimum focus position. In an embodiment, a total exposuredose accumulated in each die is within 0.9*Eo to 1.1*Eo, where Eo is anoptimum exposure dose. In an embodiment, the method includes skippingexposure operations for missing exposure fields in the exposure fieldmatrix enclosure. In an embodiment, the method includes merging steppingoperations from after a previous exposure operation to before asubsequent exposure operation into one stepping operation which movesdirectly from a previous exposure location to a subsequent exposurelocation. In an embodiment, both the exposure field corner and theexposure field matrix enclosure corner are lower left corners as viewedin plan view, the first direction is in the +x direction, the seconddirection is in the −x direction, and the third direction is in the +ydirection. In an embodiment, both the exposure field corner and theexposure field matrix enclosure corner are upper left corners as viewedin plan view, the first direction is in the +x direction, the seconddirection is in the −x direction, and the third direction is in the −ydirection. In an embodiment, both the exposure field corner and theexposure field matrix enclosure corner are lower right corners as viewedin plan view, the first direction is in the −x direction; the seconddirection is in the +x direction, and the third direction is in the +ydirection. In an embodiment, both the exposure field corner and theexposure field matrix enclosure corner are upper right corners as viewedin plan view, the first direction is in the −x direction, the seconddirection is in the +x direction, and the third direction is in the −ydirection.

Another embodiment of the disclosure is a method of manufacturing asemiconductor device, including placing a semiconductor substrate on awafer stage, wherein the semiconductor substrate has a photoresist layerdisposed thereon. A target total exposure dose for the photoresist layeris determined. A target distance separating the photoresist layer froman extreme ultraviolet mask is determined. A first portion of thephotoresist layer is exposed to a first exposure dose of extremeultraviolet radiation using a first portion of the extreme ultravioletmask, wherein the photoresist layer and the extreme ultraviolet mask areseparated by a first distance. The semiconductor substrate is laterallystepped a first time relative to the extreme ultraviolet mask. Adistance between the semiconductor substrate and the extreme ultravioletmask is changed so that the photoresist layer and the extremeultraviolet mask are separated by a second distance. The first portionof the photoresist layer is exposed to a second exposure dose of extremeultraviolet radiation using a second portion of the mask, and a secondportion of the photoresist layer is exposed to the second exposure doseusing the first portion of the mask. In an embodiment, the methodincludes laterally stepping the semiconductor substrate a second timerelative to the mask, changing the distance between the semiconductorsubstrate and the mask so that the photoresist layer and the mask areseparated by a third distance, exposing the first portion of thephotoresist layer to a third exposure dose of extreme ultravioletradiation using a third portion of the mask, exposing the second portionof the photoresist layer to the third exposure dose of extremeultraviolet radiation using the second portion of the mask, and exposinga third portion of the photoresist layer to the third exposure doseusing the first portion of the mask. In an embodiment, the methodincludes laterally stepping the semiconductor substrate a third timerelative to the mask, changing the distance between the semiconductorsubstrate and the mask so that the photoresist layer and the extremeultraviolet mask are separated by a fourth distance, and exposing thefirst portion of the photoresist layer to a fourth exposure dose ofextreme ultraviolet radiation using a fourth portion of the mask,exposing the second portion of the photoresist layer to the fourthexposure dose of extreme ultraviolet radiation using the third portionof the mask, exposing a third portion of the photoresist layer to thefourth exposure dose using the second portion of the mask, and exposinga fourth portion of the photoresist layer to the fourth exposure dose ofextreme ultraviolet radiation using the first portion of the mask. In anembodiment, the first portion of the mask, the second portion of themask, the third portion of the mask, and the fourth portion of the maskeach have a same pattern. In an embodiment, the first distance isgreater than the target distance, the second distance is less than thetarget distance, the third distance is greater than the target distance,and the fourth distance is less than the target distance. In anembodiment, the distance between the photoresist layer and the mask ischanged by raising or lowering the wafer stage. In an embodiment, a meandistance of the first distance, the second distance, the third distance,and the fourth distance is the target distance. In an embodiment, atotal of all the exposure doses received by each portion of thephotoresist layer is equal to the target expose dose.

Another embodiment of the disclosure is a method of manufacturing asemiconductor device, including in sequence: placing a semiconductorsubstrate on a wafer stage, wherein the semiconductor substrate has aphotoresist layer disposed thereon and exposing a first portion of thephotoresist layer to a first exposure dose of extreme ultravioletradiation using a first portion of an extreme ultraviolet mask. Thesemiconductor substrate is then moved relative to the extremeultraviolet mask followed by exposing the first portion of thephotoresist layer to a second exposure dose of extreme ultravioletradiation using a second portion of the mask, and exposing a secondportion of the photoresist layer to the second exposure dose using thefirst portion of the mask. Next, the semiconductor substrate is movedrelative to the extreme ultraviolet mask followed by exposing the firstportion of the photoresist layer to a third exposure dose of extremeultraviolet radiation using a third portion of the mask, exposing thesecond portion of the photoresist layer to the third exposure dose ofextreme ultraviolet radiation using the second portion of the mask, andexposing a third portion of the photoresist layer to the third exposuredose using the first portion of the mask. Then the semiconductorsubstrate is moved relative to the mask followed by exposing the firstportion of the photoresist layer to a fourth exposure dose of extremeultraviolet radiation using a fourth portion of the mask, exposing thesecond portion of the photoresist layer to the fourth exposure dose ofextreme ultraviolet radiation using the third portion of the mask,exposing a third portion of the photoresist layer to the fourth exposuredose using the second portion of the mask, and exposing a fourth portionof the photoresist layer to the fourth exposure dose of extremeultraviolet radiation using the first portion of the mask. The firstexposure dose, the second exposure dose, third exposure dose, and fourthexposure dose are each one quarter of a target total exposure dose. Inan embodiment, moving the semiconductor substrate relative to the maskincludes laterally moving the semiconductor substrate relative to themask. In an embodiment, moving the semiconductor substrate relative tothe mask includes moving the semiconductor substrate closer to orfurther away from the mask. In an embodiment, moving the semiconductorsubstrate relative to the mask includes tilting the semiconductorsubstrate relative to the mask. In an embodiment, the first portion ofthe mask, the second portion of the mask, the third portion of the mask,and the fourth portion of the mask each have a same pattern.

Another embodiment of the disclosure is a photolithography apparatus,including a radiation source, and a mask configured to modify radiationfrom the radiation source so that the radiation exposes a photoresistlayer disposed on a semiconductor substrate in a patternwise manner. Awafer stage is configured to support the semiconductor substrate. Acontroller is configured to: determine a target total exposure dose forthe photoresist layer, determine a target focus position for thephotoresist layer, control an exposure of a first portion of thephotoresist layer to a first exposure dose of radiation at a first focusposition using a first portion of the mask, control moving of thesemiconductor substrate relative to the mask, and control an exposure ofthe first portion of the photoresist layer to a second exposure dose ofradiation using a second portion of the mask at a second focus position,and an exposure of a second portion of the photoresist layer to thesecond exposure dose at the second focus position using the firstportion of the mask. In an embodiment, the mask is a reflective extremeultraviolet mask. In an embodiment, the wafer stage is configured tomove closer to and further away from the mask. In an embodiment, thecontroller is configured to control movement of the wafer stage. In anembodiment, the wafer stage is configured to move laterally with respectto the mask. In an embodiment, the controller is configured to controlmovement of the wafer stage. In an embodiment, the radiation source isan extreme ultraviolet radiation source. In an embodiment, thecontroller is configured to control an exposure of the first portion ofthe photoresist layer to a third exposure dose of radiation at a thirdfocus position using a third portion of the mask, an exposure of thesecond portion of the photoresist layer to the third exposure dose ofradiation at the third focus position using the second portion of themask, and an exposure of a third portion of the photoresist layer to thethird exposure dose at the third focus position using the first portionof the mask. In an embodiment, the controller is further configured tocontrol an exposure of the first portion of the photoresist layer to afourth exposure dose of extreme ultraviolet radiation at a fourth focusposition using a fourth portion of the mask, an exposure of the secondportion of the photoresist layer to the fourth exposure dose of extremeultraviolet radiation at the fourth focus position using the thirdportion of the mask, an exposure of a third portion of the photoresistlayer to the fourth exposure dose at the fourth focus position using thesecond portion of the mask, and an exposure of a fourth portion of thephotoresist layer to the fourth exposure dose of extreme ultravioletradiation at the fourth focus position using the first portion of themask. In an embodiment, the first portion of the mask, the secondportion of the mask, the third portion of the mask, and the fourthportion of the mask each have a same pattern. In an embodiment, thecontroller is further configured to control additional exposure stepssuch that each portion of the photoresist layer is exposed a same numberof times.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A photolithography apparatus, comprising: aradiation source; a mask configured to modify radiation from theradiation source so that the radiation exposes a photoresist layerdisposed on a semiconductor substrate in a patternwise manner; a waferstage configured to support the semiconductor substrate; and acontroller, wherein the controller is configured to: determine a targettotal exposure dose for the photoresist layer; determine a target focusposition for the photoresist layer; control an exposure of a firstportion of the photoresist layer to a first exposure dose of radiationat a first focus position using a first portion of the mask; controlmoving of the semiconductor substrate relative to the mask; and controlan exposure of the first portion of the photoresist layer to a secondexposure dose of radiation using a second portion of the mask at asecond focus position, and an exposure of a second portion of thephotoresist layer to the second exposure dose at the second focusposition using the first portion of the mask.
 2. The photolithographyapparatus of claim 1, wherein the mask is a reflective extremeultraviolet mask.
 3. The photolithography apparatus of claim 1, whereinthe wafer stage is further configured to move closer to and further awayfrom the mask.
 4. The photolithography apparatus of claim 1, wherein thewafer stage is further configured to move laterally with respect to themask.
 5. The photolithography apparatus of claim 1, wherein thecontroller is further configured to control movement of the wafer stage.6. The photolithography apparatus of claim 1, wherein the controller isfurther configured to control an exposure of the first portion of thephotoresist layer to a third exposure dose of radiation at a third focusposition using a third portion of the mask, an exposure of the secondportion of the photoresist layer to the third exposure dose of radiationat the third focus position using the second portion of the mask, and anexposure of a third portion of the photoresist layer to the thirdexposure dose at the third focus position using the first portion of themask.
 7. The photolithography apparatus of claim 6, wherein thecontroller is further configured to control an exposure of the firstportion of the photoresist layer to a fourth exposure dose of extremeultraviolet radiation at a fourth focus position using a fourth portionof the mask, an exposure of the second portion of the photoresist layerto the fourth exposure dose of extreme ultraviolet radiation at thefourth focus position using the third portion of the mask, an exposureof a third portion of the photoresist layer to the fourth exposure doseat the fourth focus position using the second portion of the mask, andan exposure of a fourth portion of the photoresist layer to the fourthexposure dose of extreme ultraviolet radiation at the fourth focusposition using the first portion of the mask.
 8. The photolithographyapparatus of claim 7, wherein the first portion of the mask, the secondportion of the mask, the third portion of the mask, and the fourthportion of the mask each have a same pattern.
 9. A method ofmanufacturing a semiconductor device, comprising: placing asemiconductor substrate on a wafer stage, wherein the semiconductorsubstrate has a photoresist layer disposed thereon; determining a targettotal exposure dose for the photoresist layer; determining a targetdistance separating the photoresist layer from an extreme ultravioletmask; exposing a first portion of the photoresist layer to a firstexposure dose of extreme ultraviolet radiation using a first portion ofthe extreme ultraviolet mask, wherein the photoresist layer and theextreme ultraviolet mask are separated by a first distance; a firstlateral stepping of the semiconductor substrate relative to the extremeultraviolet mask; changing a distance between the semiconductorsubstrate and the extreme ultraviolet mask so that the photoresist layerand the extreme ultraviolet mask are separated by a second distance; andexposing the first portion of the photoresist layer to a second exposuredose of extreme ultraviolet radiation using a second portion of themask, and exposing a second portion of the photoresist layer to thesecond exposure dose using the first portion of the mask.
 10. The methodaccording to claim 9, further comprising: a second lateral stepping ofthe semiconductor substrate relative to the mask; changing the distancebetween the semiconductor substrate and the mask so that the photoresistlayer and the mask are separated by a third distance; and exposing thefirst portion of the photoresist layer to a third exposure dose ofextreme ultraviolet radiation using a third portion of the mask,exposing the second portion of the photoresist layer to the thirdexposure dose of extreme ultraviolet radiation using the second portionof the mask, and exposing a third portion of the photoresist layer tothe third exposure dose using the first portion of the mask.
 11. Themethod according to claim 10, further comprising: a third lateralstepping of the semiconductor substrate relative to the mask; changingthe distance between the semiconductor substrate and the mask so thatthe photoresist layer and the extreme ultraviolet mask are separated bya fourth distance; and exposing the first portion of the photoresistlayer to a fourth exposure dose of extreme ultraviolet radiation using afourth portion of the mask, exposing the second portion of thephotoresist layer to the fourth exposure dose of extreme ultravioletradiation using the third portion of the mask, exposing a third portionof the photoresist layer to the fourth exposure dose using the secondportion of the mask, and exposing a fourth portion of the photoresistlayer to the fourth exposure dose of extreme ultraviolet radiation usingthe first portion of the mask.
 12. The method according to claim 11,wherein the first portion of the mask, the second portion of the mask,the third portion of the mask, and the fourth portion of the mask eachhave a same pattern.
 13. The method according to claim 11, wherein thefirst distance is greater than the target distance, the second distanceis less than the target distance, the third distance is greater than thetarget distance, and the fourth distance is less than the targetdistance.
 14. The method according to claim 11, wherein the distancebetween the photoresist layer and the mask is changed by raising orlowering the wafer stage.
 15. The method according to claim 11, whereina total of all the exposure doses received by each portion of thephotoresist layer is equal to the target expose dose.
 16. A method ofmanufacturing a semiconductor device, comprising in sequence: placing asemiconductor substrate on a wafer stage, wherein the semiconductorsubstrate has a photoresist layer disposed thereon; exposing a firstportion of the photoresist layer to a first exposure dose of extremeultraviolet radiation using a first portion of an extreme ultravioletmask, moving the semiconductor substrate relative to the extremeultraviolet mask; exposing the first portion of the photoresist layer toa second exposure dose of extreme ultraviolet radiation using a secondportion of the mask, and exposing a second portion of the photoresistlayer to the second exposure dose using the first portion of the mask;moving the semiconductor substrate relative to the extreme ultravioletmask; exposing the first portion of the photoresist layer to a thirdexposure dose of extreme ultraviolet radiation using a third portion ofthe mask, exposing the second portion of the photoresist layer to thethird exposure dose of extreme ultraviolet radiation using the secondportion of the mask, and exposing a third portion of the photoresistlayer to the third exposure dose using the first portion of the mask;moving the semiconductor substrate relative to the mask; and exposingthe first portion of the photoresist layer to a fourth exposure dose ofextreme ultraviolet radiation using a fourth portion of the mask,exposing the second portion of the photoresist layer to the fourthexposure dose of extreme ultraviolet radiation using the third portionof the mask, exposing a third portion of the photoresist layer to thefourth exposure dose using the second portion of the mask, and exposinga fourth portion of the photoresist layer to the fourth exposure dose ofextreme ultraviolet radiation using the first portion of the mask,wherein the first exposure dose, the second exposure dose, thirdexposure dose, and fourth exposure dose are each one quarter of a targettotal exposure dose.
 17. The method according to claim 16, whereinmoving the semiconductor substrate relative to the mask includeslaterally moving the semiconductor substrate relative to the mask. 18.The method according to claim 16, wherein moving the semiconductorsubstrate relative to the mask includes moving the semiconductorsubstrate closer to or further away from the mask.
 19. The methodaccording to claim 16, wherein moving the semiconductor substraterelative to the mask includes tilting the semiconductor substraterelative to the mask.
 20. The method according to claim 16, wherein thefirst portion of the mask, the second portion of the mask, the thirdportion of the mask, and the fourth portion of the mask each have a samepattern.